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Fix a bug with Barrier not being supported in Azure-qiskit #677

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Merged
lillian542 merged 9 commits into from
Jan 22, 2026
Merged

Fix a bug with Barrier not being supported in Azure-qiskit #677

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aaeb55b
skip potentially unnecessary barrier operation
DSGuala Dec 5, 2025
3adf0d6
remove instead of comment out
DSGuala Dec 11, 2025
364b831
Merge branch 'master' into skip-barrier
DSGuala Dec 11, 2025
475e16e
Merge branch 'master' into skip-barrier
DSGuala Jan 15, 2026
d64fefb
remove barrier reliance in test
lillian542 Jan 22, 2026
e78361c
black formatting
lillian542 Jan 22, 2026
fc48a86
black formatting tests
lillian542 Jan 22, 2026
3cfaee4
remove .DS_Store files
lillian542 Jan 22, 2026
0f2ee7f
changelog
lillian542 Jan 22, 2026
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5 changes: 5 additions & 0 deletions CHANGELOG.md
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Expand Up @@ -7,6 +7,11 @@
* Updated qiskit ecosystem versions: qiskit to 2.3.0 and qiskit-ibm-runtime to 0.45.0.
[(#681)](https://github.com/PennyLaneAI/pennylane-qiskit/pull/681)

* The circuit conversion from PennyLane no longer inserts a superfluous `barrier` to
delineate the circuit operations from the terminal measurements. This will allow support
for remote backends that don't support `barrier`.
[(#677)](https://github.com/PennyLaneAI/pennylane-qiskit/pull/677)

### Breaking changes 💔

### Deprecations 👋
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1 change: 1 addition & 0 deletions pennylane_qiskit/aer.py
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Expand Up @@ -16,6 +16,7 @@
evaluation and differentiation of Qiskit Aer's C++ simulator
using PennyLane.
"""

import qiskit_aer

from .qiskit_device_legacy import QiskitDeviceLegacy
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1 change: 1 addition & 0 deletions pennylane_qiskit/basic_sim.py
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Expand Up @@ -16,6 +16,7 @@
evaluation and differentiation of Qiskit Terra's BasicAer simulator
using PennyLane.
"""

from qiskit.providers.basic_provider import BasicProvider

from .qiskit_device_legacy import QiskitDeviceLegacy
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5 changes: 2 additions & 3 deletions pennylane_qiskit/converter.py
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Expand Up @@ -15,6 +15,7 @@
This module contains functions for converting between Qiskit QuantumCircuit objects
and PennyLane circuits.
"""

import warnings
from collections.abc import Iterable, Sequence
from functools import partial, reduce
Expand Down Expand Up @@ -501,7 +502,7 @@ def _function(*args, params: dict = None, wires: list = None, **kwargs):
# Processing the dictionary of parameters passed
# pylint: disable=too-many-nested-blocks
for idx, circuit_instruction in enumerate(qc.data):
(instruction, qargs, cargs) = (
instruction, qargs, cargs = (
circuit_instruction.operation,
circuit_instruction.qubits,
circuit_instruction.clbits,
Expand Down Expand Up @@ -712,8 +713,6 @@ def circuit_to_qiskit(circuit, register_size, diagonalize=True, measure=True):
for rot in rotations:
qc &= operation_to_qiskit(rot, reg, creg)

# barrier ensures we first do all operations, then do all measurements
qc.barrier(reg)
Comment on lines -715 to -716
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@lillian542 lillian542 Jan 22, 2026 •
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This and the related changes in tests/test_converter.py is the actual change. Everything else is black formatting.

# we always measure the full register
qc.measure(reg, creg)

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1 change: 1 addition & 0 deletions pennylane_qiskit/noise_models.py
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This module contains functions for converting Qiskit NoiseModel objects
into PennyLane NoiseModels.
"""

from collections import defaultdict
from warnings import warn

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1 change: 1 addition & 0 deletions pennylane_qiskit/qiskit_device.py
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This module contains a prototype base class for constructing Qiskit devices
for PennyLane with the new device API.
"""

# pylint: disable=too-many-instance-attributes,attribute-defined-outside-init,too-many-positional-arguments

import inspect
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1 change: 1 addition & 0 deletions pennylane_qiskit/qiskit_device_legacy.py
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Expand Up @@ -14,6 +14,7 @@
r"""
This module contains a base class for constructing Qiskit devices for PennyLane.
"""

# pylint: disable=too-many-instance-attributes,attribute-defined-outside-init


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1 change: 1 addition & 0 deletions tests/test_apply.py
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r"""
This module contains tests for applying operations on PennyLane IBMQ devices.
"""

import numpy as np
import pennylane as qml

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1 change: 1 addition & 0 deletions tests/test_base_device.py
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"""
This module contains tests for the base Qiskit device for the new PennyLane device API
"""

# pylint: disable=too-many-positional-arguments

from unittest.mock import Mock, patch
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9 changes: 5 additions & 4 deletions tests/test_converter.py
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Expand Up @@ -14,6 +14,7 @@
r"""
This module contains tests for converting circuits for PennyLane IBMQ devices.
"""

import functools as ft
import itertools as it

Expand Down Expand Up @@ -1722,10 +1723,10 @@ def test_circuit_to_qiskit_diagonalize_kwarg(self, diagonalize):

qc = circuit_to_qiskit(qscript, 2, diagonalize=diagonalize, measure=True)

# get list of instruction names up to the barrier (played right before measurements)
# get list of instruction names up to the first measurement
instructions = []
for instruction in qc.data:
if instruction.operation.name == "barrier":
if instruction.operation.name == "measure":
break
instructions.append(instruction.operation.name)

Expand All @@ -1745,10 +1746,10 @@ def test_circuit_to_qiskit_measurements_with_overlapping_wires(self):

qc = circuit_to_qiskit(tape, 2, diagonalize=True, measure=True)

# get list of instruction names up to the barrier (played right before measurements)
# get list of instruction names up to the first measurement
instructions = []
for instruction in qc.data:
if instruction.operation.name == "barrier":
if instruction.operation.name == "measure":
break
instructions.append(instruction.operation.name)

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1 change: 1 addition & 0 deletions tests/test_expval.py
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r"""
This module contains tests for using expvals for PennyLane IBMQ devices.
"""

import numpy as np
import pennylane as qml

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1 change: 1 addition & 0 deletions tests/test_integration.py
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Expand Up @@ -14,6 +14,7 @@
r"""
This module contains integration tests for PennyLane IBMQ devices.
"""

# pylint: disable=too-many-positional-arguments
import sys
from functools import partial
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1 change: 1 addition & 0 deletions tests/test_inverses.py
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Expand Up @@ -14,6 +14,7 @@
r"""
This module contains tests for using adjoints for PennyLane IBMQ devices.
"""

import cmath
import math

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1 change: 1 addition & 0 deletions tests/test_noise_models.py
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Expand Up @@ -14,6 +14,7 @@
r"""
This module contains tests for converting Qiskit NoiseModels to PennyLane NoiseModels.
"""

import itertools as it
from functools import reduce

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1 change: 1 addition & 0 deletions tests/test_qiskit_device.py
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r"""
This module contains tests qiskit devices for PennyLane IBMQ devices.
"""

from unittest.mock import Mock

import numpy as np
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1 change: 1 addition & 0 deletions tests/test_var.py
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r"""
This module contains tests for computing variances on PennyLane IBMQ devices.
"""

import numpy as np
import pennylane as qml

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